function Set() {
	this.content = {};
}
Set.prototype.add = function(val) {
	this.content[val]=true;
};
Set.prototype.remove = function(val) {
	delete this.content[val];
};
Set.prototype.contains = function(val) {
	return (val in this.content);
};
Set.prototype.asArray = function() {
	var res = [];
	for (var val in this.content) res.push(val);
	return res;
};